Modelling apparatus and method

ABSTRACT

A method determined a routing of data between two network elements of a telecommunications network, which are interconnected via a transmission path. The method includes identifying plurality of layers of a telecommunications model from which the transmission path is comprised, and developing a reachability table by identifying a connection between each transmission element in each layer to other transmission elements in the same or a different layer of the transmission path. For each connection defining a set of communications parameters which define a cost of communicating data via the connection and allocating a weighting value for communicating data via the connection, for all possible routes between the two network elements along the transmission path via each of the layers modelling the effect of the connection for routing the data in accordance with the set of communications parameters for the connection and determining a weighted result along each path, and combining the weighted results to determine a metric of performance for each of the possible routes. An optimum route can then be determined for routing data in accordance with for example a minimum cost metric.

FIELD OF INVENTION

The present invention relates to methods of determining a routing of data through a telecommunications network, modelling telecommunications systems, a modelling apparatus and computer programs for modelling telecommunications systems.

BACKGROUND OF THE INVENTION

Operators of telecommunications systems such as mobile radio networks and wireless access networks deploy the networks in or around places where users are likely to want to use the networks. In this way, the operators can earn income from telecommunications traffic which is communicated via their networks. In order to maximise the amount of income readily generated from a telecommunications network by a network operator it is desirable to deploy the network to provide maximum capacity when there is likely to be most demand from users. Furthermore it is desirable to deploy infrastructure equipment in an optimum way so that the cost of infrastructure can be minimised with respect to the income readily generated from users accessing the telecommunications network.

In order to assist in the planning and deployment of a telecommunications network it is known to use planning tools which provide a simulation or accounting based model of the telecommunications network based on modelling circuit calls and packet sessions generated by users accessing the network. For example, for a mobile radio network it is known to model mobile user equipment generating calls or initiating sessions and to model data communicated via the mobile radio network for each of the sessions or calls. As will be appreciated however, modelling an entire telecommunications network such as a mobile radio network can represent a computationally challenging task for a computer system, particularly, where a mobile radio network is to be modelled from end to end and at multiple layers.

SUMMARY OF INVENTION

According to an aspect of the present invention, there is provided a method of determining a routing of data between two network elements of a telecommunications network, which are interconnected via a transmission path. The method comprises

identifying a plurality of layers of a telecommunications model from which the transmission path is comprised,

developing a reachability table by identifying a connection between each transmission element in each layer to other transmission elements in the same or a different layer of the transmission path,

for each connection defining a set of communications parameters which define a cost of communicating data via the connection and allocating a weighting value for communicating data via the connection,

for all possible routes between the two network elements along the transmission path via each of the layers modelling the effect of the connection for routing the data in accordance with the set of communications parameters for the connection and determining a weighted result along each path, and

combining the weighted results to determine a metric of performance for each of the possible routes, and

determining an optimum route from the best evaluated parameters.

Embodiments of the present invention include a technique which can be used to optimise a transmission path between two or more network elements of a telecommunications network. As will be appreciated most router or switching elements perform routing or switching according to a simple set of parameters. As a result, although the transmission function can be fast, the transmission of data in terms of costs and resources may not be efficient. Furthermore, if too many parameters are taken into consideration, then the routing and switching functions may not be able to be executed quickly enough to make them effective as it could be. Furthermore a simplification of routing may solve a problem on one layer but may be less efficient at another transmission layer.

Embodiments of the present invention can provide a reliable and fast set of transmission algorithms which consider N-layers of a telecommunications model, which can be built up over time as a set of transmission routing tables and bindings. According to the present technique, a transmission function on one layer can be executed whilst applying a selection of nominated applicable constraints from nominated other layers in one step as a matrix of parameters per routing algorithm execution. The technique includes initially routing at only one layer where information is available, as would be preformed conventionally, generating a reachability table identifying each later and its rank per route which is stored in a way which can be indexed, and then using the reachability table to cross check the layers available in a given time, which has been allocated for routing in order to establish an optimum route for communicating the data. The optimisation is achieved by giving a weighting value for each connection for each transmission element at each layer to transmission elements at other layers or the same layer. The weighting function can be determined using parameters such as communications overheads consumed, delay incurred in communicating using the transmission connection, bandwidth consumed and a cost of that bandwidth, although it will be appreciated that other example parameters could be used alone or in combination to form the weighting factors.

Using this technique, an optimum route between the network elements can then be determined for routing data in accordance with for example a minimum cost metric.

Furthermore, by applying routing schemes developed using the reachability table and optimised using the weighted routing paths, a transmission routing network element in a software model can be developed and resulting tables generated and stored, with the effect that the same tables may be applied back to the real network elements with the same complex transmission function scheme. As a result, a multi-layer reachability map can be produced within the telecommunications network, without the network elements having to live route to determine an optimum transmission path and map of transmissions options. Thus a telecommunications system can be deployed already optimised by using this multi-layer routing plan and port algorithms. This is in contrast to planning a network with transmission and routing of communications between network elements without the pre-planned multi-layer routing and then determining whether the deployed system is efficient and optimising the deployed system by trial and error.

The technique is applicable to modelling tools, test equipment and vendor transmission equipment and by applying the same multi-layer reachability table driven approach to routing across all of these entity types.

In one example, the method of configuring a telecommunications system includes determining one or more optimum transmission paths between nodes as an optimisation which includes mobile standards interfaces as one layer being optimised at the same time as optimising supporting transmission layers at a lower layer. This is in contrast to optimising at the mobile layer separately to optimising each transmission layer at a time or all transmission layers together.

The present technique can therefore rapidly reduce complex multilayer computations to more simplistic weighted reachabilities which can be combined together efficiently to gain a knowledge of the overall end to end (ETE) path quality of each path in a network.

Various further aspects and features of the present invention are defined in the appended claims and include a modelling system for optimising a route between network elements of a telecommunications network.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described with reference to the accompanying drawings in which like parts are referred to using corresponding numerical designations and in which:

FIG. 1 is a schematic block diagram of an example telecommunications system which includes a mobile radio network;

FIG. 2 is a schematic block diagram representing a computer modelling tool for modelling a telecommunications system, which also appears in FIG. 1;

FIG. 3 represents an illustration of a display screen in which parts of the telecommunications system which are being modelled by the computer system shown in FIG. 1 are represented;

FIG. 4 provides a schematic block diagram illustrating a process of generating and applying a background load model to a network element within the mobile radio network;

FIG. 5 provides an illustration of a representation of a model of resources provided by a network element;

FIG. 6 is a schematic diagram illustrating a radio network area of the mobile radio network shown in FIG. 1, which is being analysed to form a shadow emulation for modelling the mobile radio network;

FIG. 7 provides a schematic representation of an application of the model of the radio network area of FIG. 6 when applied to a model of a mobile switching centre;

FIG. 8 provides a schematic representation of parts of the mobile radio network shown in FIG. 1, illustrating of process of measuring a loading at an interface between two of network elements in the mobile radio network of FIG. 1;

FIG. 9 a is a schematic block diagram of the network elements of FIG. 6, including a radio network controller; and FIG. 9 b is an illustration of an effective modelling of the radio network controller;

FIG. 10 is a representation of a graph of different parameters of network and bandwidth resources with respect to different levels of loading provided by a background node;

FIG. 11 is an illustrative representation showing a calculation of the area of a modelled cell;

FIG. 12 is an illustrative representation showing a calculation of the area of a Radio network controller (RNC) being modelled which includes seven cells;

FIG. 13 shows the modelled radio network controller of FIG. 12 with a further calculation for illustrating a process for extrapolating in the modelled network;

FIG. 14 is an illustrative representation of three modelled areas which are controlled by three radio network controllers for providing an illustration of an emulation of loading on one of the radio network controllers due to soft handover;

FIG. 15 is an illustration of the modelled areas served by the radio network controllers of FIG. 14 showing a further step in an algorithm for emulating the loading on the radio network controller;

FIG. 16 is an illustration of the modelled areas served by the radio network controllers of FIG. 14 showing a further step in an algorithm for emulating the loading on the radio network controller;

FIG. 17 is an illustration of the modelled areas served by the radio network controllers of FIG. 14 showing a further step in an algorithm for emulating the loading on the radio network controller;

FIG. 18 is a schematic block diagram illustrating elements within a modelled network element which are used to emulate a loading on that element and a propagation of loading from a south side of the network element to the north side;

FIG. 19 is a schematic block diagram of a propagation block which appears in FIG. 18 for propagating loading from a south side of the network element to the north side;

FIG. 20 is a schematic block diagram illustrating a grouping of node B's or base stations into groups or regions;

FIG. 21 is an example of the connection of the groups or regions shown in FIG. 20 in which one of the groups or regions is being processed to model the effect of that region but the remaining groups are modelled as background representations only;

FIG. 22 is a schematic block diagram illustrating connections between two mobile gateway elements via a plurality of layers of transmission layers; and

FIG. 23 is a schematic block diagram providing a simplified representation of the layers of transmission elements of FIG. 22.

EXAMPLE EMBODIMENTS OF THE INVENTION

Examples illustrating the operation of the present technique will now be described with reference to a General Packet Radio System (GPRS) network, an example of which is shown in FIG. 1. As explained above embodiments of the present invention can provide an improvement in the efficiency with which a telecommunications system is modelled and therefore the modelling of the telecommunications system can be made more accurate. As such results produced by the modelling can be used to configure the telecommunications system itself.

In FIG. 1, a conventional UMTS mobile radio network 1 is shown to include a representation of some of its component parts. In FIG. 1 mobile user equipments 2, which are conventionally referred to as mobile user equipment (UEs) are shown to be disposed in relation to Node Bs or base stations 4 with which they are communicating data to and from via a wireless access interface. As shown in FIG. 1 the Node Bs or base stations 4 are connected to radio network controllers 6 which are then connected to a mobile gateway (MGW) 8. In FIG. 1, the Node Bs or base stations 4 and the radio network controllers 6 may be disposed within one geographical region whereas the second group of Node Bs 4 and radio network controllers 6 may be disposed in another region. The mobile gateway 8 is then connected to a mobile switching centre (MSC) 10 which is connected to other core network components which form an SS7/Sigtran network 12 for communicating with other fixed and mobile access networks. Also shown in FIG. 1 is an operations and maintenance centre (OMC) 14, which is arranged to configure and control the mobile radio network 1 in accordance with a conventional operation. However, the operations and maintenance centre 14 includes a modelling device 16, which is used to model the mobile radio network. Results of the modelling process can be used to feed back to the operations and maintenance centre to configure the network dynamically as explained in the following paragraphs.

FIG. 2 provides an illustrative representation of a computer system for modelling a telecommunications system in accordance with the present technique. In one example, the computer system forms the modelling device 16 shown in FIG. 1. A CPU 20 is connected to a data store 22 which stores data and processing code for representing a telecommunications system. Also connected to the CPU 20 is a dynamic RAM 24 in which the variables and computer program code for representing a model of the telecommunications system are stored whilst being executed by the CPU 20. The parts of the model are created by selecting preferable representations of the different parts of a telecommunications system and connecting them together as represented on a display screen 26. As represented in FIG. 2, an example of parts of the telecommunications system of FIG. 1 which might be produced and modelled by the computer system are displayed in a more detail on the display screen 26.

As shown in FIG. 2 different component parts of a mobile radio network are connected together within a particular region as represented on the display screen 26. Thus lines 30, 32, 34 represent a boundary of a particular region which is modelled by the computer system. As shown in FIG. 3 Node B or base stations 4 are represented by a graphical symbol and disposed within the geographical region which is represented by the lines 30, 32, 34. In addition a graphical representation of a radio network controller 6 is disposed in the group geographical region and connected to the base stations 4. A graphical representation of a mobile gateway 8 is shown connected to the radio network controller 6 and is also again connected to a core network part 12. Thus underlying the graphical representation of each of the components of the mobile radio network shown in FIG. 2 is corresponding computer code which represents the processing of data communications to and from each of those parts in accordance with the operation of those parts in the real world.

Chunking Technique

A large data model of 12 Gbytes can be used in one example by an application running on a system with limited local live storage (e.g. Random Access Memory: RAM) of only 4 Gbytes and addressable and sizeable non-live storage (eg: Hard Disk Drive: HDD) of say 100 Gbytes.

In order to render a near real time graphical experience for the user of the network model the use of large amounts of Virtual RAM is not an attractive option.

The system is therefore broken down into groups of logical data entities as Network Elements and Bearer interconnects. However loading thousands of Node Bs or BTS' into the system would use up many Gbytes of memory and leave little room for program tasks thereby constraining the application and the operating system and resulting in a slow experience for the user when using the application.

As explained by the following sections, according to the present technique each base station/NodeB is instantiated in the model as a chunk with node level information listing: key ports, network element and mobility parenting and load per interface node and connection level Information which adds the details of the entities bearers virtual links and Full Build level information which lists all of the entities physical details as well.

The present technique aims to calculate the load impact of a network element or a group of network elements, for example the base stations in a mobility region (LA1) connecting to a radio network controller (RNC) and to calculate a full build of a radio network controller, which is required to support the base stations.

If all of the network model including all of these entities were to be loaded for every such task, task execution would be slow. On the other hand, if only the affected entities are loaded up for this task, but without a representation of the other entities around the ones under consideration then all interactions are not modelled correctly in the application and so errors would frequently be experienced.

Using the proposed method, the task for an envisaged UMTS example is operated as follows:

i) The full model of the RNC under analysis is loaded into RAM memory as: one Chunk, Chunk-Level (All).

ii) Partial models of the NodeBs to be modelled in less detail are loaded in groups or Regions as N×Chunks, M×Regions, Chunk-Level (Node).

iii) The remaining network entities such as mobiles generating load and other core network elements which source and/or sink load are accounted for using background loads.

In this way a good representation of the subject (the RNC), its impacting peers (Node B groups) and its surrounding Regions (core network or other RANs for example) are included/accounted for in the execution task, but a much reduced fraction of the total data model content is required to be loaded into RAM than would normally be required.

This method is envisaged for modelling mobile communications systems where one domain of the model may have a large number of instances and a low level of detail as compared to another domain of the model that has fewer instances but each instance is far more complex to model. Hence, the large difference in scope and resolution detail in modelling both domains in the same end-to-end model can be addressed. In order to achieve a variation of modelling domains, the modelling device 16 utilises techniques which can represent a traffic profile as an effective consumption of network services and transmission bandwidth and furthermore the traffic profile can be propagated to other network elements. Furthermore a group of network elements can be represented as a shadow of itself, which can be used to provide a difference in modelling resolution as explained above. Finally a technique for determining an optimum route via a transmission path between two network elements can be used in assisting a configuration of routing and switching of data at multiple layers.

Load Modelling

In order to achieve the chunking arrangement of the model it is necessary to utilise a technique for representing a group of elements as accurately as possible. In some examples, the modelling system shown in FIGS. 1, 2 and 3 uses a moveable background load generator or background node. This technique enables a user to apply a background load emulation in a structured manner anywhere in a telecommunications system being modelled and to scale and translate the load produced as necessary to account for frame and protocol overheads as well as an estimate of signalling stream overhead in an automated manner. The load model is controlled and parameterised by a software interface which analyses and emulates a plurality of simple data communications streams in detail and then replicates these simple models by address to emulate a real composite load of many users. The background load emulation technique is illustrated in FIG. 4.

FIG. 4 provides an example representation of process steps and calculations used to form a background load generator or “background node”. In FIG. 4 three different traffic profiles 40, 42, 44 are specified by a user for forming the background load generator 46. Each of the traffic profiles 40, 42, 44 includes a plurality of mobile services 48 each of which identifies a type of service which will correspond to a mobile communication session. For example, the type of service could be data communications, voice call, text or video communications. Thus within each traffic profile there is specified a plurality of different mobile service types for each of the corresponding mobile communication sessions represented by the traffic profile. Each of the traffic profiles 40, 42, 44 are combined to form a background load generator in which the mobile services are amalgamated. The background load generator is then applied to a network element 50 in an application step 52.

In the application step 52 the mobile services are converted to a representation of consumed network services as the combined traffic profiles are translated into an effective usage of an available amount of network services which can be supported by the element network 50, which is being modelled. The representation of the mobile services and the translation process is illustrated more specifically in FIG. 5.

As the background node is movable its emulation effect is also translatable across a number of network elements in a given system. This technique can be applicable to both the test industry and the vendor equipment industry where self test is an essential function for modern equipment.

In FIG. 5 the amalgamated mobile services from the traffic profiles 40, 42, 44 are represented in the mobile service layer 60. Thus the mobile services layer 64 is formed from a combination of the mobile services specified for the traffic profile 62. The effect of the mobile services is then translated into the mobile layer 64 as the network services are consumed. For example the effect of the mobile services would represent an increase of protocol overheads, frame overheads and signal streaming overheads, which are a specified resource of the network element being modelled. Correspondingly, the effect of the network services consumed in the mobile layer 64 can be translated into the use of physical layer resources 66 for each of the physical layer transport types available to the network element such as asynchronous transfer mode (ATM), internet protocol (IP), PDH/SDH, optical, copper etc. Finally at the bottom layer of the physical layer 68 the effect of the consumed network resources converts to a physical bit rate which represents a consumption of an available bit transmission rate on an interface from the network element 46 to a network element to which that network element is connected. Thus in combination, the mobile services, network services and the demand from the physical layer according to a given traffic profile form a combined loading element LE. The effect of the consumed network services and transmission bit rate is represented by the connection from the network element 50 to a subsequent network element 54 which for the example shown in FIG. 4 is a mobile switching centre. Thus as represented from the connection between the network element 50 and the mobile switching centre 54 a translation of the background load generator is represented by the network services consumed 56 and the transmission bandwidth consumed 58. Thus according to FIG. 4 the background load generator 46 which represents a collection of traffic profiles can be applied to a network element 50 and the effect of that application represented by both network services consumed 56 and a transmission bit rate consumed 58 when connecting the network element 50 to the mobile switching centre 54. The translation process from the network element 50 to the mobile switching centre 54 can be referred to as “propagation” of the background node.

Network Shadow Emulation Technique

According to one technique used by the modelling tool 16, which allows for a computationally efficient model to be formed, a moveable background load is used in association with an emulation of a number of other network elements in order to emulate the sum of a background load source and sink, combined with the effect of having several other network elements present without having to actually fully model them or represent them with real equipment. As such, for example a whole radio network area may be represented by one model emulation or emulator with the same software to represent many other nodes and to represent real traffic sources and sinks.

A group of equipment forming a region covered in the mobile radio network is emulated by first modelling the network elements and external interfaces polled whilst the network elements are simulated at different load levels. Over several runs of a background node(s), which is used to stimulate the modelled network elements a data-set which represents the effect of load changes at the region's external interfaces according to different stimuli is obtained which can be referred to as “a shadow characterisation” of the region of equipment to be represented. Thereafter the whole area and its composite source/sink background load may be represented by a single entity with the same external ports as the original (model or real equipment), which can be referred to as a shadow emulation version which is a dynamic model. Furthermore, by analysing the shadow characterisation dataset and generating a set of algorithms to represent the load measured during characterisation according to input background load settings, it is possible to generate using extrapolation of these algorithms an emulation outside the bounds of the original characterisation.

This may be applied to a model or a real piece of transmission equipment as a mechanism employed by that transmission equipment as an intelligent routing scheme. An example illustration of the shadow characterisation technique and the shadow emulation of a group of network elements is explained in the following paragraphs.

In FIG. 6 the background node formed in FIGS. 4 and 5 is used to load each of three Node B's 80, 82, 84 in accordance with the traffic profile specified for the background load generator 46. Thus applying the background load generator 46 to each of the Node B's 80, 82, 84 can represent a loading of that traffic profile on a radio access interface, such as the UTRAN, within a particular geographical area in which the Node B's 80, 82, 84 have been deployed. Using the application of the background node 46 to each of the Node Bs, an effective consumption of network services and transmission can be determined for each of the Iub interfaces between the Node B's 80, 82, 84 and a radio network controller 86 to which they are connected. Furthermore, in accordance with the present technique the network services consumed and the transmission bandwidth consumed can be propagated from the radio network controller 86 to the output of the radio network controller on the IuCSinterface 88 between the radio network controller 86 and a mobile gateway to which it is connected (not shown). Thus effectively using the background load generator 46, a particular geographical area within a mobile radio network can be modelled by applying the background load generator 46 to each of the Node B's. A propagation process is then applied to propagate the network services and transmission bandwidth used from the Node B's to the radio network controller 86 and correspondingly to the output of the radio network controller 86 on the interface IuCS88, between that radio network controller 86 and a connecting MSC. Thus effectively as shown in FIG. 6 the background node 46 has been used to model a radio network area of the mobile radio network in terms of a loading applied to an MSC. The modelled network area can thereby be represented as a shadow model.

Correspondingly in FIG. 7 a loading can determined for an MSC 90 by representing the radio network area 89 shown in FIG. 6 and applying that to each of a plurality of connections to the MSC 92, 94 by representing the shadow emulation model formed for the radio network area shown in FIG. 6. Thus effectively the combined loading can be translated in accordance with the formula 96 shown in FIG. 6 to make an effective loading on the MSC 90. Likewise that loading can be modelled at an output of the MSC 98.

Results determined from the modelled shadow emulation can be verified, by taking real measurements from the network being modelled. For example, having developed the shadow emulation, a loading on an interface can be determined, for example the Iub interface, between a Node B and a radio network controller to provide, a resulting network services and transmission bandwidth consumed. This loading can be confirmed by analysing a real network. As shown in FIG. 8, a radio network controller 102 and an MSC 104 are shown. A probe 106 can be used to measure signalling and data communicated, which can be interpreted as consumed network services and transmission bandwidth for a traffic supported by the mobile radio network, which corresponds to a model traffic profile which has been represented in a background node 46. As such measurements can be used to verify a loading on a real network with respect to the modelled network and then an adjustment can be made in terms of the actual resources consumed by that traffic profile.

As a consequence of forming a shadow characterisation of a section of a radio access network 89 as shown in FIG. 6, a range of results can be generated off line and stored and used to apply to the model of the entire system on line. Such an arrangement is illustrated in FIGS. 9 and 10. In FIG. 9 a the Node B's 80, 82, 84 as represented in FIG. 6 are shown connected to the radio network controller 86. As already explained a background node 46 can be applied to each of the Node B's to represent a loading in accordance with a predetermined traffic profile. Thus a loading at the input of the radio network controller can be translated into a loading at the output. Thus as shown in FIG. 9 b for a given range of traffic profile loading at the input load 120 of the radio network controller 86 on the Iub interface a resulting loading on the IuCSinterface 122 upstream of the radio network controller 86 can be represented by a result in upstream load 124. In operation off line results can be generated for a loading on the IuCSinterface 122 with respect to an input in accordance with the traffic profile as represented in FIG. 10. A traffic profile for the IuCS example here would include Mobile to Mobile Calls, Mobile to Land Calls, Short Messages and Circuit switched data plus this user planes according Signalling load. In FIG. 10 for each of a plurality of for traffic profile loadings, a result in determination of each of a plurality of parameters are determined, three of which are illustrated in FIG. 10. The parameters may be for example a number of bearers used 130, an amount of protocol overheads 132 and an amount of signalling stream channels occupied 134. Thus the off line results can then be applied elsewhere in the model to represent a range of possible effects on the interface upstream of the radio network controller 122 for different traffic profile loadings.

As will be appreciated, the example provided here is illustrative only, whereas the overall principle of the present technique is applicable to both GSM, GPRS, UMTS, HSDPA, and the EPS and other mobile system evolutions.

Example Loading Emulation: Soft Handover

A topology logical grouping for modelling network elements in accordance with the present technique, can be used to form within a model of a telecommunications network groupings of self-similar nodes such as:

-   -   a “ring” of Cross Connects     -   a ring of Optical cross connects     -   a set of STPs operating as an STP SS7 Network     -   a reliable cluster such as a number of MSCs operating with a         number of mobile gateways (MGW) that act as a redundant pool.

Here a specific example is provided for soft handover. An emulation of loading on a particular network element can be achieved for mobile nodes conducting a soft handover process between areas, which are covered by a particular RNC. An amount of mobile UE that are engaged in soft hand and roaming from one RNC area to any neighbouring areas is determined in accordance with the following explanation. This represents one example of a load on a network element and as will be appreciated there are other types of loading depending on what is being modelled.

Transform logic can then be used to apply the soft handover loading to other network elements and the effects of source loading, sp as to propagate a load from one network element to another or one side of a network element to another. A soft hand-over algorithm is illustrated as follows:

FIG. 11 provides an illustration of a cell coverage area. Based on a given radius r, the cell coverage area can be calculated as:

Cell coverage area=πr²

FIG. 12 illustrates the calculation of the RNC coverage area which can be determined as:

RNC coverage area=(Number of cells of the RNC)×(Cell coverage area)=(Number of cells of the RNC)×πr ²

The coverage area for the RNC is then determined as shown in FIG. 13, for a radius of the RNC coverage area R as:

RNC coverage area=πR ²=>RNC radius=√((RNC coverage area)/π)

Soft handover is a technique in which the mobile UEs are communicating with two cells contemporaneously as the mobile moves from one cell coverage area to another. For the present example we consider the case where a loading is caused by mobile UEs moving from one RNC area to another. An RNC which covers a network area to which the mobile UEs are roaming to is referred to as a control RNC and the RNC from which the mobile UE's are roaming is referred to as a drift RNC. Mobile UEs which are disposed between two RNC areas are those which are engaged in a soft hand-over process. These areas are shown in FIG. 14 as SA1 and SA2 for a control RNC RNC_c and first and second adjacent RNCs RNC1, RNC2. FIG. 15 illustrates an example of a relative distribution of overlapping coverage areas SA1, SA2 are assumed to be served by a fraction of the cell area of two serving cells C1, C2. The overlapping area served by the first cell c1 is assumed to be 70% of the cell radius, so that:

Overlapping area SA1=π0.3r²

Whereas for the second cell c2, the overlapping area is assumed to be 30% of the cell area, so that

Overlapping area SA2=π0.7r²

In order to estimate the loading which is caused by soft handover from the adjacent cells on the target control RNC_c it is necessary to determine first the loading caused by mobile UEs that only this RNC RNC_c is serving. An area A1 shown in FIG. 16 is considered to represent a region within which mobile UEs are only served by the control RNC RNC_c and are therefore not involved in the soft handover process. The area within which mobile UEs are not involved in a soft handover from adjacent cells is therefore determined with respect of a radius R2, which is a fraction of the total RNC coverage area radius R. Thus for the target RNC, RNC_c, the radius R2=R×fraction, so that the area which includes mobile UEs which are not taking part in soft handover becomes:

Non soft handover area=πR2²

From this calculation it is possible to determine as a fraction the coverage area for which loading is being induced as a result of mobile UEs engaging in soft handover, namely

soft handover area fraction=(RNC coverage area−non soft handover area)/(RNC coverage area)

FIG. 17 then shows the soft handover traffic from the control RNC RNC_c to the adjacent RNC, RNC1, RNC2, which can then be determined as:

NS(SHO_Egress)·Ld(i)=NS(SHO_Prop)·Ld*(Drift_Amount/100)*Circumference_(—) i/sum(Circumference_(—) i).

In this expression, “Drift Amount” represents a proportion of the traffic generated by the mobile UEs for the particular RNC for which the Egress or out board traffic is being modelled. The Drift Amount will be different depending on the location of the RNC and is set empirically from experience and observing real world conditions. For example if the RNC is at a board of a country then the drift amount will approximately 10%, but if the RNC is within a country at a remote location then the drift amount will be 2-3%.

The NS(SHO_Egress) is the loading on the network services as a result of the egress of traffic from the target RNC. This is a function of the network services which are propagated to the RNC which is based on the soft handover area fraction, which is worked out for the fraction of mobile UE traffic which is considered to be engaged in soft handover as established above. Thus the network services which are represented by this traffic as the soft handover area fraction is determined and applied to this part of the equation.

The fraction of Circumference_i/sum(Circumference_i) provides an empirical determination balancing the amount of the mobile traffic which is egressing from the RNC being modelled with respect to all of the RNCs that are surrounding that target RNC. Accordingly a fraction of the egress traffic is determined with respect to the ingress traffic from the surrounding RNCs. This calculation has been determined from an observation of real world results with respect to results modelled using this expression.

According to this expression, the network services NS can be determined as a function of a loading for a given soft handover egress loading, a drift amount and the circumference of the RNC area. Using this expression each background load may be loaded onto multiple network element services (NES) at multiple networks. Furthermore, each traffic model may be loaded with a weighting of 0-100% such that the N×Traffic models all add up to a 100% loading, but the service loading within each traffic model is able to be set independently.

For this example “algorithm” for soft handover a trial with specific input loads can be used to determine the load on the network element and the output interface which can then be extrapolated. The following section explains the termination of network services NS and the propagation of the network services to other network elements based on a function of the network element being modelled.

Example of Transform Logic

FIG. 18 provides an example illustration of how transform logic is used to convert loading of resources from one side of a network element NE, which is referred to as a south side to another side of the network element NE referred to as a north side. In accordance with the function of the network element NE, the south and north sides may include both input and output interfaces.

As an example, we consider the RNC 89. As shown in FIG. 6, at the south side of the network element NE a loading elements LEs are provided, on from each of the Node b's 80, 82, 84, which are terminated within the RNC 89 at a termination block TRM. The termination block TRM is arranged to translate the received loading from the south side Les, which are corralled from the Node B's 80, 82, 84. Only the network services NS are corralled because the other loading elements of the mobile services MS and the physical layer demand D, can be determined from the network services alone. The network services NS are combined by the NS terminate block TRM and then passed to a propagation block PRP for translating into the north side loading element LEn and the weighting on the RNC 89 itself, which is represented by a NS weight block WGT.

The network services propagate block PRP is arranged to apply transform logic on the received combined network service loading from the NS Terminate block TRM to propagate the network services loading NS(prop). This will include determining a loading on protocol stacks and resources consumed by the network element being modelled and also the extent to which the modelled network will load the network services at the output of the network element. For the example of the RNC 89, the network services consumed as a result of the propagation to the north side will depend on and will be a function of the Ius interface. The process of propagation will also determine a weighting on the network element itself, which represented by the NS weight WGT.

A network services transmit block TRT translates the output of the propagation block PRP into the loading element on the north side LEn, which can be represented by the transmitted network services NS(TXM) and mapped into the equivalent mobile services MS and the physical layer resources D.

An example of the transform logic, which is used to propagate loading elements from the south side to the north side, is shown in FIG. 19. As shown in FIG. 19, the south side loading element LEs components, mobile services MS, network services NS, and physical layer resources Demand, are fed from the termination block TRM to the transform logic TL, which adapts the loading caused by the loading element LEs on the network element itself and the loading on the north side loading element LEn in accordance with the function and operation of the network element as explained above. The transform logic may work on the network services only, but may take into considerations in some functions the other loading elements MS and D.

As illustrated by the example for soft handover egress for an RNC, a combination of empirical functions and analytical techniques can be used to generate the transform logic which converts an input load on network services to a load on the network element concerned and the load on the output interface of the network element.

Chunking Examples

As explained above, the present technique provides a way of modelling the mobile radio network shown in FIG. 1 in a way which improves the scope and resolution requirement of each of the components of the network whilst reducing the amount of processing power required to compute the model and also an amount of memory occupied by the model at any one time. To this end, for example each of the base stations/Node Bs shown in FIG. 1 may be divided into different groups. In one example some of the different groups represent different regions. FIG. 20 provides an example illustration of a grouping of base stations or Node Bs into three groups 160, 162, 164 which are connected correspondingly to an access network and then to a corresponding radio network controller. Each of the Node Bs is located at an individual site which is represented by a corresponding population of users and therefore a relative loading or amount of traffic generated from those users can be represented from that site. As shown in FIG. 21 the Node Bs which are grouped into the three regions are processed by the model representing each of the Node Bs and each of the groups to represent the total amount of traffic and loading caused by the Node Bs on corresponding communications channels 170, 172, 174 which connect the groups of Node Bs to an access network 180 and radio network controllers 182, 184 and correspondingly mobile gateways 186, 188 which are then connected to a core network 190. The radio network controller 182 and mobile gateway 186 may serve a first region for example “Manchester” and second radio network controller 184 and the second mobile gateway 188 may serve a second region for example “Newcastle”. Therefore other parts of the telecommunications system served by other regions for example “Bristol” and “London” 92, 94 maybe correspondingly represented by the model.

According to the present technique as illustrated in FIG. 21 the Node Bs illustrated in FIG. 20 are grouped into regions. Accordingly, each region is modelled for a first time period within which a relative loading which each of those regions causes on the traffic communicating within that region with the corresponding access network and radio network controllers 82, 84 is determined. Therefore for a next time period the loading which that network produces on the connecting channel is modelled without processing a model of each of those Node Bs and the traffic produced by the corresponding mobile user equipments which are communicating with the Node Bs. Thus as illustrated in FIG. 21 only the region for Manchester 60 is currently being modelled in detail where as the remaining regions 162, 164, are modelled in background that is to say modelled as a shadow emulation using the technique described above to represent the loading produced within a previous time interval during which those regions were modelled in detail. Thus according to the present technique the computer system is arranged to load the models for the Node Bs into memory to be processed by the CPU for a time period only for the Node Bs associated with region 60 whilst the remaining regions are represented as an extrapolation or an interpolation of the loading produced when those regions were previously modelled. Thus each of the regions is cycled through in turn for respective time intervals by loading the regional model into RAM 4 and processing the model using the CPU 1 and representing each of the remaining groups or regions as a loading based on the loading produced previously when that region was loaded into RAM 4 and processed by the CPU during a previous time period.

Multi-Layer Modelling Technique for Optimised Routing Using Linked Layer-Reachability Tables

The modelling system 16 may also include a technique which can be used to identify an optimum transmission path between two or more network elements of a telecommunications network. For most router or switch cases, these elements route or switch according to a simple set of parameters. These parameters can be a limited subset of a set of parameters which characterise only the layer at which the transmission function (route/switch) is being applied. As a result, although the transmission function is very fast, the transmission of data in terms of costs and resources may not be cost effective. Furthermore, if a transmission scheme were overly complex requiring too many parameters to be processed per transmission function, then the transmission function may be cumbersome and slow despite potentially being very well bound to the transmission action being performed.

Often oversimplification of routing solves a problem well on one layer but is less efficient as an N-Layer transmission solution.

What is needed is a reliable and fast set of transmission algorithms which consider N-Layers of a telecommunications model, which can be built up over time as a set of transmission routing tables and bindings. According to the present technique, a transmission function on one layer can be executed whilst applying a selection of nominated applicable constraints from nominated other layers in one step as a matrix of parameters per routing algorithm execution. The technique includes the following steps:

-   -   Step-1: Initially route at only layer where information is         available (as before)     -   Step-2: As more information about the network is generated at         each network element, then a Reachability Matrix per modelled         layer and each rank per route is stored and indexed.     -   Step-3 Future transmission function executions cross check the         layers available in the given time allocated for routing within         the end to end (ETE) delay constraints for this transmission         network element.

Furthermore, by applying these complex routing schemes at a transmission routing network element in a software model and storing the resulting tables generated, then the same tables may be applied back to the real network elements with the same complex transmission function scheme. As a result, a multi-layer reachability map will be produced within the telecommunications network, without the network elements having to live route to determine an optimum transmission path and map of transmissions options. Thus a telecommunications system can be deployed already optimised by using this multi-layer routing plan and port algorithms. This is in contrast to planning a network with transmission and routing of communications between network elements without the pre-planned multi-layer routing and then determining whether the deployed system is efficient and optimising the deployed system by trial and error. Furthermore, a multi-layer table driven system is much faster than a purely mathematical algorithm.

The technique can also be deployed to avoid shared fate issues of planning multiple routes for reliability at layer N but then mapping them unaware to the same bearer at layer N−1.

The technique is applicable to modelling tools, test equipment and vendor transmission equipment and by applying the same multi-layer reachability table driven approach to routing across all of these entity types then a Policy Control Entity (PCE) system may be employed either operating by centrally check-pointing all transmission nodes to a central table repository system or by a future system of inter-transmission routing query messages from to a router.

A term that is emerging for network elements that can operate at multiple layers is a Multi-Service Platform or (MSP).

FIG. 22 provides an illustrative representation of two elements in a mobile radio network which may be modelled by the modelling tool 16 shown in FIG. 1. According to the present technique the modelling system 16 is arranged to perform the multi-layer route planning for communicating between two network elements. As shown in FIG. 22 a first mobile gateway 200 may be connected to a second mobile gateway 202 via a connecting interface 204. However a virtual transmission route may represent the communication of signalling and data between the mobile gateway 200 and the mobile gateway 202 which effectively forms an interface for transmission of the signalling and data between the two mobile gateways 200, 202. The virtual transmission path may be comprised of a plurality of elements which are connected at each of a number of different layers. For the example shown in FIG. 13 there are four such layers, which may correspond to a layered telecommunications model. A first layer includes an add drop multiplexer (ADX) 210 as second layer in an intellect protocol (IP) connection 212 a third layer is another add drop multiplexer (ADX) 214 and finally a fourth layer uses an optical multiplexer which performs a transmission function 218 for data at the physical layer. A connection between the add drop multiplexer (ADX) 210 and the internet protocol (IP) layer 212 may be via ATM 220 whereas a connection between the internet protocol layer 212 and the add drop multiplexer 214 may be via TCP/IP 232. Finally, again the connection between the second add drop multiplexer 214 and the optical multiplexer 218 may be via ATM 224.

Correspondingly, a second group of transmission elements may be provided at a plurality of different layers for the second mobile gateway 202 in order to complete the transmission path between the two mobile gateways 200, 202. For this example, there are correspondingly four layers, which provide an add drop multiplexer 310, an internet protocol (IP) layer 312 and an add drop multiplexer 314. A further optical multiplexer 318 is provided at the physical later and is connected to both the add drop multiplexers 214, 310. Furthermore, each of the network elements are linked by transmission channels in correspondence with the first group of elements. Thus the layer three add drop multiplexer 310, the layer two internet protocol router 312 and the add drop multiplexer 314 are link by transmission links 320, 322, 324. In addition, it is also possible for the transmission elements from the first group 210, 212, 214 to be linked by transmission channels 326, 328, 330, 332, 334, 336 from the second group 310, 312, 314, because transmission of data from one layer may be made to transmission elements at another layer via more than one route to more than one network element. Thus in effect the communication of data between the two mobile gateway network elements can be via several different paths between the transmission elements in the four example layers illustrated in FIG. 22.

FIG. 23 provides a simplified representation of the transmission elements shown in FIG. 22, which are arranged to communicate data between the two mobile gateway transmission elements. In FIG. 23, two example paths are shown between the two mobile gateways 200, 202. The first path includes transmission channel links A.1, A.2, A.3, A.4, A.5, A.6, A.7, A.8. The second path includes the transmission channel links A.1, B.2, B.3, B.4, B.5, A.6, A.7, A.8. Each of the communications links can be labelled in this way to assist on determining an optimum path for data transmission between the two mobile gateway nodes 200, 202.

For each of the paths, weightings are determined in accordance with one or more optimisation functions. Typically, three or four optimisation functions are optimised at a time. The Optimisation functions are a set of generic optimisation algorithms of which there are many, but the inputs to these algorithms are derived from the model constructs such as connectivity, cost of physical objects supporting paths (connectors, bearers maintenance of objects such as transmission equipment, etc) and all of which are used by communicating using that connection.

The present technique provides an arrangement for optimising a transmission path between the two mobile gateway elements 200, 202 where a plurality of different layers in which different components may be available for communicating. Thus, there may be more than one path through a layer of network elements which may or may not be more efficient. The optimisation is determined in accordance with the following steps:

-   -   The reachability matrix is determined for each element at each         layer which identifies the other elements in the layer or a         different layer which can be reached from the transmission         element.     -   Each path to each layer on the reachability matrix for each         connection from a component is then weighted in accordance with         a pre-defined metric. The metric may represent a cost in terms         of network resources or transmission bandwidth required to         connect one network layer with another.     -   For each of all possible paths for communicating between two         network elements a combined weighted sum is formed for that         transmission path.     -   Finally an optimum path between two network elements is         determined from the weighted sum.

Typical Optimisation Function Examples are:

-   -   i) Cost of Reachability from this node to Reachable node in         terms of equipment and maintenance of equipment to support     -   ii) Delay incurred by services along each path     -   iii) Number of nodes traversed     -   iv) Number of layers of transmission technology traversed         (usually there is more processing involved and hence more cost         the more layers are traversed on the path)     -   v) Transmission functions operated along the path, for example         number of QoS mappings incurred, eg: UMTS, DS, MPLS is more         complex than a mapping set of UMTS to fixed and pre-defined MPLS         profiles.

Embodiments of the invention may be used in the construction of a tool platform having a database which includes all network elements as multi-layer representations that may be grouped into regions such as MSC parented, or RNC parented, LA, RA, URA mobility parented. Additionally the regions would be able to be operated with background loads representing each region for some optimization tasks.

Various modifications made to the embodiments described above without departing from the scope of the present invention. For example although the present invention has been illustrated with reference to modelling a mobile radio network such as GPRS or UMTS, it will be appreciated that the other telecommunications system can be modelled in this way such as a wireless access network Wi-Fi or indeed any fixed interne protocol broadband or other telecommunications network. Various further aspects and features of the present invention are defined in the appended claims. 

1. A method of determining a routing of data between at least two network elements of a telecommunications network, which are interconnected via a transmission path, the method comprising identifying a plurality of distinct transmission layers of a telecommunications model from which the transmission path is comprised, developing a reachability table by identifying a connection between each transmission element in each layer to other transmission elements in the same or a different layer of the transmission path, for each connection defining a set of communications parameters which define a cost of communicating data via the connection and allocating a weighting value for communicating data via the connection, for all possible routes between the two network elements along the transmission path via each of the layers modelling the effect of the connection for routing the data in accordance with the set of communications parameters for the connection and determining a weighted result along each path, and combining the weighted results to determine a metric of performance for each of the possible routes, and determining an optimum route from the best evaluated parameters.
 2. A method as claimed in claim 1, wherein the defining a set of communications parameters comprises identifying one or more communications resources available for communicating data and signalling via the connection, determining an amount of the communications resources consumed for communicating the data via the connection, and evaluating a cost of the communications resources to form the weighting value.
 3. A method as claimed in claim 2, wherein the communications resources include one or more of communications overheads, delay incurred in communicating using the transmission connection, bandwidth consumed and a cost of the bandwidth, and the evaluating the cost to form the weighting value includes scoring the consumed communications resources with respect to a value of the communications resource.
 4. A method as claimed in any preceding claim, wherein each new network element addition to the telecommunications network is optimally matched into the telecommunications system at a time of application in order to maintain required performance for least cost.
 5. A method as claimed in claim 4, wherein the addition of a network element to the telecommunications network is determined in accordance with network equipment and bearers.
 6. A method as claimed in any preceding claim, including determining one or more optimum transmission paths between the network elements as an optimisation which includes mobile standards interfaces as one layer being optimised at the same time as optimising supporting transmission layers at a lower layer.
 7. A method as claimed in any preceding claim, including applying offline from the telecommunications network performance and configuration data extracted from the real telecommunications network, and after the determining the optimised route from the best evaluated parameters, generating re-configuration data for the telecommunications network to either enhance the performance of the telecommunications network or enable parts of the telecommunications network to be retired or re-used elsewhere after optimisation due to the optimisation requiring fewer resources than before optimisation.
 8. A method as claimed in claim 7, including applying on-line as part of the telecommunications network implemented as a distributed optimisation algorithm, with parts of the overall optimisation algorithm deployed at each of the network elements within the telecommunications network which have a capability to be able to support the algorithm parts and that through distributed control communications interfaces can both calculate optimisation coefficients to improve performance against a set of defined driver optimisation functions and over time improve the configurations stored on these nodes to improve performance and/or reduce resource impact on the network and free up equipment or reduce the need to purchase more equipment as the network load grows.
 9. A modelling system for determining a route for data between at least two network elements of a telecommunications network, the at least two network elements being interconnected via a transmission path, the modelling system being arranged in operation to identify a plurality of distinct transmission layers of a telecommunications model from which the transmission path is comprised, to develop a reachability table by identifying a connection between each transmission element in each layer to other transmission elements in the same or a different layer of the transmission path, for each connection to define a set of communications parameters which define a cost of communicating data via the connection and allocating a weighting value for communicating data via the connection, for all possible routes between the two network elements along the transmission path via each of the layers, to model the effect of the connection for routing the data in accordance with the set of communications parameters for the connection and determining a weighted result along each path, to combine the weighted results to determine a metric of performance for each of the possible routes, and to determine an optimum route from the best evaluated parameters.
 10. A modelling system as claimed in claim 9, wherein the modelling system is arranged to define a set of communications parameters by identifying one or more communications resources available for communicating data and signalling via the connection, determining an amount of the communications resources consumed for communicating the data via the connection, and evaluating a cost of the communications resources to form the weighting value.
 11. A modelling system as claimed in claim 10, wherein the communications resources include one or more of communications overheads, delay incurred in communicating using the transmission connection, bandwidth consumed and a cost of the bandwidth, and the evaluating the cost to form the weighting value includes scoring the consumed communications resources with respect to a value of the communications resource.
 12. A modelling system as claimed in claim 9, 10 or 11, wherein the modelling system is arranged to match each new network element addition to the telecommunications network at a time of application in order to maintain required performance for least cost.
 13. A modelling system as claimed in claim 12, wherein the addition of a network element to the telecommunications network is determined in accordance with network equipment and bearers.
 14. A modelling system as claimed in any of claims 9 to 13, wherein the modelling system is arranged in operation to determine one or more optimum transmission paths between the network elements as an optimisation which includes mobile standards interfaces as one layer being optimised at the same time as optimising supporting transmission layers at a lower layer.
 15. A computer program providing computer executable instructions, which when loaded on a data processor performs the method according to any of claims 1 to
 8. 16. An apparatus for determining a routing of data between at least two network elements of a telecommunications network, which are interconnected via a transmission path, the apparatus comprising means for identifying a plurality of distinct transmission layers of a telecommunications model from which the transmission path is comprised, means for developing a reachability table by identifying a connection between each transmission element in each layer to other transmission elements in the same or a different layer of the transmission path, for each connection means for defining a set of communications parameters which define a cost of communicating data via the connection and allocating a weighting value for communicating data via the connection, for all possible routes between the two network elements along the transmission path via each of the layers means for modelling the effect of the connection for routing the data in accordance with the set of communications parameters for the connection and means for determining a weighted result along each path, and means for combining the weighted results to determine a metric of performance for each of the possible routes, and means for determining an optimum route from the best evaluated parameters. 